Many biomedical tests and experiments rely on the visual assessment of cell and molecular activity of samples located on a holder such as microscope slide, Petri dish and the like. Some such activity produces photon emission as a natural consequence of the activity under review and in other studies molecular and cellular changes can be observed by the addition of material which will generate photonic emission such as is obtained using so-called lux, luc and phot gene technology.
Thus in the general fields of genetic engineering and molecular biology the study of gene expression, gene deletion and gene insertion has involved the addition of genetic material which will generate photon emission from genetically manipulated cells, using so-called lux gene expression, and such techniques have been used in the fields of virology, molecular biology, immunology, microbiology and cell biology.
Using apparatus as described PCT published specification WO88/04045, it should be possible to observe lux gene expression from molecular and cell activity at a very much earlier point in the reaction than has hitherto been the case, due to the great sensitivity of such apparatus. In particular it should be possible to identify the position of photon emission due to the lux gene expression from single cell locations, thereby allowing tests performed on very small samples of material and in very much smaller periods of time than hitherto. However if an ordinary Petri dish or microscope slide is employed as the sample holder, it is not possible to provide the perfect optical coupling needed between the photon emitting material of the sample and the input face of the fibre optic entrance window of the image intensifier, since the base of an ordinary Petri dish and the material of an ordinary microscope slide is not in the form of a fibre optic face plate.
It has been proposed to overcome this problem in the aforementioned PCT specification by forming the base of the Petri dish or the microscope slide from fibre optic glass and placing the underside of this material in intimate contact with the input window (also of fibre optic glass) of the image intensifier.
Whilst this should reduce the degredation of resolution in transferring light emanating from photon emitting sites onto the image intensifier, it has been found in practice that perfect contact is not always possible between the molecular or cellular material of the sample and the upper face of the sample holder, so that even when the latter is formed from fibre optic glass, serious resolution degredation results, due to spreading of light as it travels from the material in the sample to the fibre optic glass of the sample holder. This becomes particularly noticeable when the depth of the sample material becomes significant.
It is an object of the present invention to overcome this problem.
It is another object of the invention to provide improved methods of cell and molecular investigation which follow from the use of the improved light transfer system of the invention.